Grasso’s proposal would relocate the second trading floor of 11 Wall St. to a location in the suburbs – a move the exchange says could keep the world’s biggest stock market up and running even if its famed Wall Street headquarters is destroyed in a terror attack.

“We are considering establishing a second active trading facility,” an NYSE spokesman said. “Westchester is among the possibilities we are considering.”

Some city officials speculated that the move was in retaliation for the Bloomberg administration slashing in half the $900 million then-Mayor Rudy Giuliani promised to help NYSE get a bigger facility across the way at 23 Wall St.

“If we find more money for the exchange, the backup facility goes away,” one city official told The Post.

Grasso gave a July 10 briefing to NYSE members on the proposal.

A spokesman for the mayor said “the exchange has not indicated to us that they are interested in moving to Westchester,” but a NYSE rep insisted they have told “all appropriate parties.”

Mitchell Moss, an NYU professor and adviser to the mayor, said Grasso “is trying to get New York City to build him a Taj Mahal paid for by the taxpayers.”